应用中断时间序列方法评估干预措施对陆家嘴水厂出厂水三卤甲烷的影响
Assessment of intervention measures on trihalomethane in finished water by interrupted time series analysis
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摘要:
背景 青草沙水库面临着水藻繁殖、富营养化的问题，由此引起水中的氯化消毒副产物含量增加一直是人们关注的重点。
目的 评估“青草沙水库藻类监测与应对方案”（后称“方案”）的实施对常规处理出厂水中三卤甲烷（THMs）的治理效果。
方法 从2011—2019年，每个季节采集陆家嘴水厂1次出厂水水样，每次采集1个样品，检测出厂水中四种THMs（三氯甲烷、二氯一溴甲烷、一氯二溴甲烷、三溴甲烷）的质量浓度（后称浓度）。以2014年“方案”的实施作为干预分界点，将整个研究阶段分为干预措施实施前（2011—2013年）和实施后（2014—2019年）两个阶段。应用中断时间序列分析方法进行分段线性回归，评估干预措施实施前后出厂水中THMs浓度和变化趋势。
结果 在“方案”实施前，时间每延长一个季节，出厂水中总THMs浓度上升1.561 µg·L−1（
P =0.010），最高浓度达25.97 µg·L−1。干预措施实施后，出厂水中总THMs的浓度变化未见统计学意义（P =0.198）；但出厂水中总THMs浓度回归线的斜率为-0.626（P =0.001），即THMs浓度随时间变化呈下降趋势。自2017年起至2019年，陆家嘴水厂出厂水中THMs的平均浓度保持在10 µg·L−1以下。结论 青草沙水库藻类和富营养化治理措施达到了较好的效果，将出厂水中的THMs控制在较低水平，THMs的变化趋势由干预前的逐年上升，变为干预后的逐年降低。
Abstract:Background The Qingcaosha Reservoir is facing issues of algal blooms and eutrophication, and the resulting increase in the level of chlorination disinfection by-products in the water has been a major concern.
Objective To evaluate the impact of "Algae Monitoring and Control Program in Qingcaosha Reservoir" (hereinafter referred to as the program) on the control of trihalomethanes (THMs) in conventional finished water.
Methods From 2011 to 2019, water samples were collected from the Lujiazui Water Plant once per season, one sample each time, and the concentrations of four THMs (trichloromethane, dichlorobromomethane, monochlorodibromomethane, and tribromomethane) were measured in the samples. Using 2014 when the program was implemented as a cut-off point, the entire study period was divided into two phases: pre-implementation (2011–2013) and post-implementation(2014–2019). Segmented linear regression with interrupted time series analysis was applied to assess the concentrations and trends of THMs in the finished water before and after the program launch.
Results The concentration of total THMs in finished water increased by 1.561 µg·L−1 (
P =0.010) for each season of time extension before launching the program. The change in the concentration of total THMs in finished water was not statistically significant after the program launch, but the THMs concentration showed a decreasing trend as the slope was −0.626 (P =0.001). From 2017 until the end of 2019, the average concentration of THMs in finished water of Lujiazui Water Plant dropped to 10 μg·L−1 or less.Conclusions The algae and eutrophication control measures in Qingcaosha Reservoir have achieved good results, controlling THMs in finished water at a low level, and the trend of THMs has changed from a yearly increase pattern before the program to a yearly decrease pattern after the program.
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